History of Life

But 1st an Intro Video

Timeline• Big Bang: ~13.75 bya (billion yr ago)

– or 13.75 Ga Giga = Ga = 10^9– or 433.6 x 10^15 seconds (SI base unit)

•

• Milky Way Galaxy: ~13.2 bya

• Sun: ~4.57 bya

• Earth: ~4.54 bya

• Moon: ~4.53 bya, ~30–50 mya after the Solar System

Formation of Galaxies

~ 1 billion years after the Big Bang...

Some clumps of matter dispersed by their internal motions, others grew by attracting other nearby matter.

Surviving matter clumps became the beginnings of today's galaxies.

When a clump becomes massive enough, it starts to collapse under its own gravity & becomes a protogalaxy.

Galaxies & Within (intragalaxies)

large groupings of stars, dust, and gas held together by gravity

contain all the familiars: billions of stars, some with planets, moons, comets, asteroids.

& the less familiar: nebulae, neutron stars, black holes, and dark matter

The Milky Way: Our galaxy

1 ly = ~10 trillion km (10^16 m) = ~ 6 trillion miles

Within the early Milky Way:

Nebula: giant clouds of

gas,

dust,

&

the birthplace of stars

Crab Nebula in visual spectrum from Hubble telescope

Nebular Theory:

The theory that explains the formation of Earth and it’s solar system.

The Earth, like all the other planets, formed out of the disk of gas and rocks that orbited the sun.

If the Earth was made out of a bunch of chunks of rock that collided and stuck together... what would it be like inside?

4.54 bya, when Earth had reached it’s final size, it was a hot and lifeless planet.

Formation of Earth's Moon

continuous bombardment by meteorites, and intense volcanism

4.1 bya - 3.8 bya: Late Heavy Bombardment at the end of the Hadean Eon

Achaean EonEarth has significantly cooled, no stable atm, no O2, no O3

LIFE?

End of Part 1